Studies of ultrastructural changes occurring after erythropoietin administration and the modulating effect of hypertransfusion on the response to erythropoietin. Negative contrast studies of solubilized membrane protein material from normal erythrocytes. Studies of the appearance of echinocytes in the blood of patients in various disease states. Initiation of studies to determine whether ultrastructural changes follow the administration of chemotherapeutic agents used for the treatment of acute leukemia.